Antioxidant responses of damiana (Turnera diffusa Willd) to exposure to artificial ultraviolet (UV) radiation in an in vitro model; part II; UV-B radiation

Introduction: Ultraviolet type B (UV-B) radiation effects on medicinal plants have been recently investigated in the context of climate change, but the modifications generated by UV-B radiation might be used to increase the content of antioxidants, including phenolic compounds. Objective: To generate information on the effect of exposure to artificial UV-B radiation at different high-doses in the antioxidant content of damiana plants in an in vitro model. Methods: Damiana plantlets (tissue cultures in Muras-hige-Skoog medium) were irradiated with artificial UV-B at 3 different doses (1) 0.5 +/- 0.1 mW cm(-2)(high) for 2 h daily, (2) 1 +/- 0,1 mW cm(-2) (severe) for 2 h daily, or (3) 1 +/- 0.1 mW cm(-2) for 4 h daily during 3 weeks. The concentration of photosynthetic pigments (chlorophylls a and b, carotenoids), vitamins (C and E) and total phenolic compounds, the enzymatic activity of superoxide dismutase (SOD, EC 1.15.1.1) and total peroxidases (PDX, EC 1.11.1), as well as total antioxidant capacity and lipid peroxidation levels were quantified to assess the effect of high artificial UV-B radiation in the antioxidant content or in vitro damiana plants. Results: Severe and high doses of artificial UV-B radiation modified the antioxidant content by increasing the content of vitamin C and decreased the phenolic compound content, as well as modified the oxidative damage of damiana plants in an in vitro model. Conclusion: UV-B radiation modified the antioxidant content in damiana plants in an in vitro model, depending on the intensity and duration of the exposure.